Variable cam



ov 25, 1958 .l R. H. BAKER 2,861,470

VARIABLE'CAM Filed April 15. 1955 face 26 is slidably mounted on -United VStates ,Patent C VARIABLE CAM Ray H. Baker, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware This invention relates to an adjustable cam mechanism and more particularly to an adjustable cam mechanism Maving a continuous cam surface defined by a number of cams adjustable with respect to each other.

The v present invention provides an adjustable cam mechanism suitable for use ina number of installations where it is desirable to have `a variable continuous cam operating or actuating surface. i f v yOne particular use of this cam mechanism is in the fuel ilow control ofra gas turbine engine. The cam mechanism adjusts the fuel flow according to a xed schedule as the power lever or throttleis moved through its selection range. However, each engine has different operating-characteristics, so that a particular schedule may be suitable for one engine and unsuitable-for another engine. The adjustable cam mechanism of this inventionvprovides flexibilityY in the fuel ow adjustment pattern sorthat the schedule can beY varied according to the operatingcharacteristics of the individual engine. Thus, theV schedule can be varied at one or more desired points in the throttle selection range, such as the idling point, without changing the remainder of the schedule. The primary object of this'invention is to provide a continuous cam surface dened by a :number of cams adjustable with respect to each other.

This and other objects of this invention will be readily apparentfrom the following specilicationanddrawings, in which:

Figure l is a sectional view of a portion of a turbine fuel control embodyinga cam nechanism according to thisinventiongand l j ,Figure 2 isa transverse sectional View on the plane indicatedlby" line 2 2 of Figure l f Referring now to. Figure .l of thev drawings, a shaft 2 is rotatably supported within housing .portions 4 .and 6 by bearings 8.. and 10.. The .outer race of bearing 8 `is located byA circular shoulder. 12.. of vhousing portion 4. and retainedlin place. .by split ring 14... The inner race of bearing 10' is locatedby.. circular .sh ulder 16 of shaft .2

"*and retained inplaceby .split .ring`18 tting Withina 'cylindrical groove. .in -the shaft... and housing portion 20 are all part of the same housing, bint only those portions of the housing necessary to the description of this invention have been shown.

' A cam 22 having a sleeve portion 24 and a cam surshaft 2. Another cam 28 having a sleeve portion 30 and a cam surface 32 is slidably mounted on cam 22 so that the cams are mounted coaxially on the shaft in telescopic relationship. The sleeve portion 24 of cam 22 is provided with an axially elongated diametrical slot 34, and a similar axially elongated diametrical slot 36 is formed in shaft 2. A pin 38 xed to sleeve portion 30 of cam 28 extends through the elongated slots in the shaft and cam 22.

Referring now to Figure 2, it can be seen that the width of the slots is equal to the diameter of the pin, so that the circumferential relationship between the cam sleeves .Housing .portions-4. andl "6 t 28 with respect to 2. and the shaft remains xed at all times. However, cam 28 is slidable with respect to cam 22 and the shaft, and likewise cam 22 is slidable with respect to both cam 28 and the shaft. The cam surfaces 26 and 32 of the cams form a continuous cam actuating or operating surface 40 which is variable by axially adjusting either cam 22 or the other cam. The variable continuous cam surface 4t) actuates a cam follower 42 xed to a movable member 44 which controls the throttle valve opening.

Shaft 2 includes a splined portion 46 on which is mounted an arm of the power lever linkage (not shown) to interconnect the shaft and theV power control lever.

As the power control lever is moved through its power selection range by the operator to set the fuel flow to the engine, shaft the set fuel ow to the engine is adjusted according to a xed schedule by the continuous cam surface 40 actuating cam follower 42. If a single cam were used, the set fuel flow to each engine would be adjusted according to the same fixed schedule, regardless of the individual operating characteristics of the Yparticular engine. However, each particular engine vhas individual operating characteristics and it isdesirablethat the schedule of fuel ow adjustment be variable to best suit the needs ofthe particular engine. As alreadyl described, each of the cams 22 and 28 is adjustable with respect to theV other cam axially of shaft 2 so that the continuous cam surface 40 can be varied. Thus, if it is desirable to adjust the fixed schedulein the idle range, a portion of cam vsurface 26 can be substituted for cam surface 32 by axially adjusting 3. within the recess.

either ofthe cams. Each of the cams can be adjusted to set the'xed schedule of adjustment, best suited-to the needs of the particular engine.

' Cam 28 is adjusted as follows: A bushing 47 has a threaded portion 48 cooperatinggwith a similar threaded portion yin housing portion 20 to locate the bushing within the housing. An O-ring seal 50 fitting within'an annular groove 52 of the bushing provides a seal between the bushing and the housing. An anti-friction washer 54 fits between the sleeve portion 30 of cam 28 and the Lbase 56 vof bushing 47 to` adjust the cam axially as the bushing is threaded into and out of the housing. The bushing includes a threaded shank portion 58 of reduced diameter andV a number of Spanner holes 59 for a spanner wrench to adjust the bushing. A lock nut .60 litting on the threaded shank portion 58 and bearing against housing 20 retains the bushing in place after the bushing and cam have been adjusted. f

' Cam 22 'is adjusted as follows: A conical Ycoil spring 62 bears against the end of shaft 2 and the base 63 of sleeve portion 24 of cam 2,2 to bias the cam within the housing. The bas'e 63 is provided with a circular recess 64, and a circular bossf66 on the end of a threadedstud 68 lits The threaded stud v68V fits within a partially'threaded bore 70'in bushing 47, an O-ringseal 72 being provided between the stud and the bore. The position of cam 22 is adjusted by threading stud 68 into and out of bore 70, with a lock nut 76 bearing against bushing 47 being used to retain the stud in place after the stud and cam have been adjusted. Stud 68 includes an Allen wrench socket 69 to provide for adjustment of the stud.

As will be apparent, cam 28 is adjusted relative to the housing and shaft 2, and cam-22 is adjusted relative to cam 28. By a suitable combination of adjustments, both cams may be adjusted to any combination of positions axially of the shaft within the range permitted by the structure.

Thus,

2 and cams 22 and 28 are rotated, and

this invention provides a cam mechanism having cations` may be made within the scopeY arid 'spiritj'jf th;

inventionl I claim:A 1. An adjustable cam mechanism comprising, in combinaim am annular nemberhav'ing mainly fric*m cam surface, a second annular member located lin telef-* scopic relationship with saidrst 'annular member and having-an vaxially facing cam surface disposedin radially" adjacentY relationship to said cam surface of said first arinular member whereby said clam surfaces form a' continuous cam surface having portions thereof defined' by each'of saidl cam surfaces, a pin secured to' one of said members and projecting diametrically with respect thereto, axially extending slot means in the other of said annular members `for receiving said pin and having an axial length greater than the diameter of saidpin whereby saidi members areinterconnected for conjoint rotational movement thereof but are axially adjustable with respect'r to each other, andLmeans for axially adjusting each of said. annular members with respect tothe other annular' member", to adjust the axial position of the cam surface of the annular member being adjusted with respect to the camsurface ofthe other annular` member to thereby vary said continuous ,cam surface by varying that portion of the continuous cam surface definedY by the cam surface of the member being adjusted, f

2.Y Anadjustablecam mechanism comprising, in combinagtion, a, Shaft, arst annular member slidablymounted, on saidjshaftgand having an` axially facingcam surface, ay second `annular memberuslidably mounted on said shaft intelescopic relationship with said firstannular member andV having an axially facing cam surface disposed in V said cam surface of;l saidradially adiacsst relationship to first annular member whereby said cam surfaces forma continuous, cam surfacehavingportions thereof defined byeach of said camr surfaces, elongatedslot meansin saidshaft and inthe radially inner annular member, pin means supported by the radially outer annular member.

and extending through said slot means, the width ofsaid slot means being substantlally equal to the width of said pin means whereby said members are interconnected for conjoint rotational movementand the length of said slot means being greater,k than the width` of said pin means whereby each of Asaid annular members is axially adjust?` able with respect to the other` annularmember,` and means for axially adjusting each of said annular: members with respect to theV other annular member to adjust the axial position of the cam surface of the member being adjusted with respect to the cam surface of the other annular member to thereby vary said continuous cam surface by varying that portion of thecontinuous cam surface defnedby thelcam Surfaceof thememberbeing adjustedon, saidl Ysh ft a1 Second annular 'membersldablyimounted 'an S,

attelage aisecond section defined ing the proportion of the total in telescopic relationship with said first annular member Aand havingan axiallyI facing cam surface disposed in radially adjacent relationship to said cam surface of said first annular member whereby each of said cam surfaces forms a continuous cam surface having portions thereof defined by each of said cam surfaces, a housing, each of said annular members having a sleeve portion fitting within said housing, means within s aid housing bearing against the sleeve portions of each of said annular members and adjusting the axial position of each annular member with* rielpectto the other annular member toV adjust the axial Vposition of the cam surface of the one annular member being ladjusted with respect. to the cam surface of the other annular mernber'toy thereby vary said continuous cam surface by varying that, portion of the continuous cam surface defined by the cam surface of the member being adjusted, and means fixing the angular relationship of said members with respect to each other.

' 4f. An Vadjustable cam mechanism comprising, in cornbination, afir'stannular member having an axially facing cam "surface, a second Vannularmember located in tele# scopic relationshipv with said iirst annular member and having an axially facing cam surface disposed in radially adjacentrelation'ship to said cam surface of said first annular member whereby said cam surfaces form a continuous cam'surface, said continuous cam surface having a totaloperative surface divided into a first section defined by an'operative portion of one of said cam surfaces andv by an operative portion of the other of 'saidcam surfaces, a shaft for supporting said an` nular`member`s, means fixing the angular relationship ofi saidmembers with respect to each other vand to said shaftv for conjoint rotational movement thereof, means for varycam surface formed by said first section and said second section, said last mentioned mea'ns including means for axially adjusting one of said annular members with respect'to the other annular member and to said shaft toadjust the axial position of the camvsurface f said one annular member with respect-to. the cam surface of the otherl annular member to vary the'v sizes of the operative portions of said cam surfaces and thereby VaryA the proportions of the total surface formed by each of said sections.

References Cited in the le of this patent UNITED STATES PATENTS 64,922- Strickland May. 21, 1867` 1,331,746 Evenson Feb. 24, 1920 1,336,803 Woerner Apr. 13, 1920 1,460,651 Hall July 3, 1923: 1,506,851. Martin et al Sept. 2, 1924 2,107,079 Mentele Feb. 1, 1938 2,167,921 Watson Aug. 1, 1939 2,216,318Y Lewis Oct. 1, 1940 2,445,902, Bell v- July 27, 1948: 2,591,650 Williams -.--1. Apr.V 1', 1952! 2gl7i9- -Morrisonl L.. Nov.y 11', 1957r` 2,618,764 Rieber i.;g. Nov. 18, 1952; 

